Conventionally, various techniques for updating map information stored in a navigation apparatus have been developed.
One exemplary navigation apparatus disclosed in Japanese Patent Application Publication No. JP-A-2003-302225 is structured as follows. When any need to store new map data arises during operations, whether or not there are any free areas in a storage unit is detected. When the storage unit has no free areas, the map data stored in the storage unit is deleted based on the usage history information of the map data so as to create a free area. The new map data is then stored in the free area created in this manner.
However, with the navigation apparatus disclosed in Japanese Patent Application Publication No. JP-A-2003-302225, whenever no free areas are found in the storage unit, a free area is created so as to store therein the new map data. This invites an inevitable problem of an increase in file fragmentation of map data that reduces speeds in reading the map data.